rivt is an extensible, open source tool for writing and organizing engineering documents as text, HTML or PDF files (referred to as rivt docs). A rivt doc is generated from a rivt file (.py) that includes rivt markup and imports the rivtlib Python package. Multiple rivt docs in a rivt folder may be compiled and linked into a rivt report. This site is an example of an HTML rivt report.
An interface for finding public rivt files on GitHub is here and a collection of open source models and calculations on Google Drive, including rivt, is here.